The present invention relates to a dental appliance for introducing a filler material into tooth cavities.
More particularly, it relates to a dental appliance which has a filler pipe, a filler expelling element which is reciprocable in a first passage and merges into the filler pipe, a replaceable magazine which extends transversely to the filler pipe and opens into the latter so that a part of the filler material such as amalgam is pressed from the magazine via a second passage by a magazine expelling element in a working stroke which starts above the opening of the magazine and ends at the outlet of the filler pipe, so as to press the part of the filler material into the filler pipe. A mechanical transmission couples the filler expelling element and the magazine expelling element surrounded by a common housing so as to coordinate their movements. The transmission includes a toothed rack which is connected with the magazine expelling element, an expelling lever which is turnably connected with the housing and has a free end engaging in the toothed rack, an expelling button which is actuatable by a finger and connected with the filler expelling element, and a projection. The lever is arranged so that during the working stroke it displaces with the toothed rack via the expelling button and the projection in direction toward the filler pipe before the front end of the filler expelling element reaches at the upper end of the opening of the magazine into the filler pipe. This dental appliance is disclosed in the above identified U.S. patent application.
In the above described dental appliance, the fingeractuatable expelling button moves always parallel with and relative to the filler expelling element. This means that a pure translatory movement is possible, which is performed by the forward and rearward stroke of the finger of the operator, for example by the indicating finger.
It has been found that under certain conditions it can be not favorable ergonomically when the operator in addition to the required translatory movement of the filler expelling element with the finger, performs a pressing movement upon the expelling button.